1. Field of the Invention
The present invention concerns a balance in which the weight force of a load to be weighed is introduced through a load receiver that is constrained in parallel-guided motion by two guide links extending in parallel at a distance from each other, each of the guide links being connected at one end to the load receiver and at the opposite end to a stationary part of the balance. The load receiver is guided in relation to the stationary part of the balance in a parallel-displacement mode within the plane of the parallelogram that is defined by the four ends of the guide links. The balance has a force transducer to convert the weight force into an electrical signal and a lever mechanism for transmitting the weight force from the load receiver to the force transducer with a first and a second lever as well as a mechanical coupling area for the releasable connection with a calibration weight., The first lever has an input arm extending from a coupling that introduces the force from the load receiver and is formed on a load receiver portion facing the stationary part to a first support that serves as lever fulcrum and is formed on a portion of the stationary part facing the load receiver; and the first lever also has an output arm extending from the support in the direction towards the stationary part. Receiving the force through a coupling from the output arm of the first lever, the second lever is held by a second support serving as lever fulcrum formed on a portion of the stationary part facing the load receiver; and the second lever also has a portion that extends in the direction towards the load receiver and serves to further transmit the weight force to the force transducer.
2. Description of the Related Art
In a known balance of this kind (DE 196 05 087 A1) whose lever mechanism has a total of three levers for the successive reduction of the weight force introduced into the load receiver, the coupling area that serves for the connection of the calibration weight is arranged on an arm of the third lever that is coupled to the second lever (the third lever following the second lever in the force reduction chain). A small calibration force introduced to this coupling area thus corresponds to a weight force on the load receiver of a multiple amount that is determined by the reduction ratio of the lever mechanism. Therefore, by using this arrangement of the coupling area, the application of a relatively large weight force to the load receiver may be simulated by a calibration weight of desirable small size. In particular, with a calibration weight corresponding only to a small fraction of the capacity load of the balance, it is possible to perform a calibration as if a full load were placed on the balance.
However, with this simulated application of the full capacity load it is not possible in the calibration process to cancel errors in the lever ratio occurring in those levers of the mechanism that precede the lever that is equipped with the coupling area. Over the course of the lifetime of a balance, lever ratio errors of this kind can easily develop because the levers that follow the first lever are supported and coupled to each other by very delicate, thin flexure pivots that can suffer deformations when the balance is subjected to shocks.